The pre-spawning concentrations of Euphausiacea, in particular of Meganyctiphanes norv- 

 egica, are encountered as early as the latter part of February. 



These crustaceans are represented in the plankton catches only by individual specimens, 

 but they were found in large numbers in the stomachs of individual herring (up to 65 specimens, 

 according to data by V. A. Rudakova). 



Two to three weeks later- -in the second half of March- -spawning concentrations of Calanus 

 finmarchicus are formed in the coast waters of the southern and central regions of the Norwegian 

 Sea. 



The development of phytoplankton and the spawning of Euphausiacea are regarded by us as 

 the first indications of the biological spring. Usually these phenomena were first observed in the 

 coast regions in the southern part of Norway. The eggs and nauplii of Euphausiacea were encoun- 

 tered in plankton. 



The spawning of Calanus finmarchicus begins in the latter part of March and in April in the 

 Atlantic waters, which iiave a temperature of 7° and in the mixed waters (with a considerable ad- 

 mixture of Atlantic waters) that have a temperature of 4-5° (Figure 3 a, d). During this period, the 

 principal mass of crustaceans is concentrated in the 0-10 m. layer. As a result of this, the bio- 

 mass there rose to 400-500 mg/m^- During the biological spring, the quantity of plankton is in- 

 creased abruptly and its composition becomes more varied. For instance, the following organisms 

 were encountered at station No . 262 in the waters of the Norwegian current north of the Faroes on 

 March 31, 1954, in the 0-25 m. level: 



Calanus finmarchicus - V and VI copepod stages Few 



Nauplii Calanoida Solitary specimens 



Calanus finmarchicus - l-II-III stages " 



Pseudocalanus elongatus Very few 



Spinocalanus abyssalis Solitary specimens 



Oithona similis 



Oikopleura labradoriensis 



Thysanoessa inermis 1 specimen 



At 50-100 m., besides the crustaceans enumerated above, the following were encountered, 

 namely: Metrldia longa, Metridia venusta, Ostracoda varia , Meganyctiphanes norvegica, Oithona 

 atlantica, the pteropod mollusk Limacina retroversa and the chaetognatha: Sagitta elegans and 

 and Eukrohnia hamata . 



The vernal biological processes are considerably delayed in the central and northern regions 

 of the Norwegian Sea as well as in the vicinity of the East Icelandic current . At the time when the 

 nauplii and young of Calanus appear in the Atlantic waters near the shores of Norway in the latter 

 part of March and in the early part of April, no concentrations of plankton are observed in the upper 

 layers at the edge of the cold East Icelandic current in spite of a considerable admixture of warm 

 waters (temperature of 7° on the surface )(Figure 3 c). Calanus finmarchicus of the VI copepod 

 stage adds a slight increase to the biomass of plankton in the 50-100 m. layer at a temperature of 

 4-5 . At a depth of more than 300 m. (below the thermocline) the cold-loving Calanus hyperboreus 

 of the VI copepod.stage predominates in the plankton. 



In view of the fact that the maturing of Calanus begins during the wintering in deep waters, 

 the temperature of the deep waters greatly influences the time of the formation of pre -spawning 

 concentrations; the warming of the surface layers, so it seems, is of secondary importance. A 

 similar phenomenon was observed by us on April 7, 1954, at station No. 274 (Figure 3c) at the edge 



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